In order to store digital electronic data, it is known to use magnetic tape data storage cartridges which are inserted into a tape drive unit having magnetic recording and reproducing heads. Typically such magnetic storage devices are used for recording back-up data generated by a host computer programmed to control the data recording process.
In recording a sequence of data sets onto a magnetic data recording medium such as the tape in a tape cartridge, it is conventional to provide the host computer with an early warning of the end of the recording medium (EWEOM). The position of the EWEOM has to be chosen judiciously so as to avoid writing data beyond the capacity provided by the recording medium and yet avoid unnecessarily limiting the capacity of the recording medium to record data.
Some data processing operations require that the data to be recorded is copied from one recording medium onto another recording medium. Such operations may, for example, be required to make an archive record or to provide a back up of data to be used at a plurality of different sites. A problem arises in the case of magnetic storage tapes because the data storage capacity of a tape may vary due to a number of factors, including the magnetic recording quality of the tape, and of the drive and a combination of the two. The nominal capacity of two tapes may be the same but they may actually vary in capacity by up to 5 to 10%.
This means that the ability to perform a tape to tape copying operation may be compromised if the source tape from which the data is to be copied is filled up to or close to its capacity. This is because the destination tape onto which the data is to be recorded may not have a capacity sufficient to receive all the data.
A prior solution to this problem has been to make the position at which the EWEOM is given to the host further removed from the real end of medium position on the tape. This only helps if the host performing the tape to tape copying operation continues recording on the target tape after the EWEOM has been reported to the host. This solution runs the risk that the real end of medium position will be encountered and at this point the copy operation will have failed.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.